It’s a hot August morning at a vineyard in Davis and the air smells like cinnamon. The spice is one of the main ingredients of the polymer-based solution being sprayed over the grapes by a slow-moving tractor.
Usually, this product is used as a barrier against fungus. But today, researchers with UC Davis are testing to see if it might help protect the grapes from wildfire smoke.
During a break at the site of the experiment, Naomi Kampen, a UC Davis graduate student lending a hand in the experiment, described the taste of smoke-tainted wine. It’s no one’s favorite, and like many others present that day, she said she’s tasted it far more often than she would like.
“The thing that I pick up most in the really bad smoke tainted wines is stale cigarette smoke,” Kampen said. “Like if you’ve had a night of drinking and you’ve smoked a bunch of cigarettes and then you wake up in the morning, smell your hands, and regret your entire life.”
While researchers haven’t figured out exactly how it happens, what they do know is this: When smoke from severe fires settles over a vineyard, the grapes draw it in. When those grapes are turned into wine, it creates a flavor that is, at best, a little smoky and at worst, tastes like an ashtray.
But with that impact on one of the state’s most iconic industries has come funding for researchers seeking to remedy the problem. In a couple of weeks, Kampen says the Davis team of researchers will return to the vineyard and cover a number of the grapes in a cloud of smoke. After that, they’ll turn the grapes into wine and test how effective the spray was at reducing the level of smoke taint.
“I don't think any of us are hugely optimistic that this will be the silver bullet, but it could be a piece of a larger mitigation attempt,” Kampen said.
Anita Oberholster, a wine researcher with UC Davis who’s leading the August trial, and many others focusing on smoke taint, said previous testing has found similar sprays only offer about 10% protection for grapes against smoke exposure. Even so, she said winemakers are desperate for any help that they can get, however small.
“They just want to do something to feel like they're protecting their grapes,” she said.
A search for answers
Research on smoke taint is pretty new. The first academic paper on the topic came out of Australia about two decades ago. But at the time, many researchers didn’t know the issue would become as widespread as it has in recent years.
“I don't think back in those mid-2000s that I ever anticipated it was going to be this much of a problem,” said Kerry Wilkinson, a professor of enology at the University of Adelaide in Australia and one of the first researchers to study the topic.
With climate change and the presence of more frequent fires, Wilkinson said there’s no doubt anymore that this problem will persist.
“As we've seen growing seasons experience warmer temperatures on average, less rainfall, we've got drier, warmer conditions,” she said. “Not surprisingly, we've seen the occurrence of…more severe bushfires and increased frequency.”
Although research on smoke taint in the United States began years before 2020, it wasn’t until massive fires hit California that year that the winemaking community here began to understand the enormity of the issue. Oberholster said she has seen a boost in interest and funding since then. Most recently, in June, California Senator Alex Padilla introduced a bill in Congress that could provide over $32 billion for research over five years.
So far, some of the research has looked at what can be done to protect the grapes before smoke hits, like sprays. But Oberholster says the most promising solutions are those that treat wine made from tainted grapes through methods like reverse osmosis.
“It's going to be very hard to find a solution in the vineyard that's very practical and not too expensive,” she said. “It will be very valuable to get a treatment option that… can actually treat wine and not impact the overall quality greatly, so that wine can actually be sold, and perhaps sold in the bracket it was aimed for originally.”
In the meantime, winemakers have tried a variety of methods to mitigate the flavor impacts that come with using tainted grapes. Some have turned to making lighter wines, like a rosé, reasoning that perhaps limiting the amount of time that tainted grape skins sit with the rest of the fruit’s juice will prevent the wine from taking on that smoky flavor. But more recent research suggests this may not be as effective as once hoped.
“You really can't make the skin contact time short enough to completely prevent that from happening,” said Tom Collins, a wine researcher at Washington State University.
He now recommends that winemakers make the wine they were originally going to make anyway.
“It'll probably have more smoke-related issues, but let's try to mitigate those after the fact,” he said. “If you make a wine in a lighter style, there are less other things present in that wine to maybe mask some of the impact of the smoke.”
Oberholster said she sees her work with sprays as another piece of this conversation. Sometimes manufacturers of sprays will bring their products to her and ask if she can test them to see if they might be good barriers against smoke taint, as well.
“A lot of what I do is also just screening, even if I, as a researcher, don't think there will be a lot of efficacy,” she said.
A changing climate for winemakers
Deb Cahn and her husband Ted own Navarro Vineyards, located in Mendocino County’s Anderson Valley. Her first experience with smoke taint came earlier than most, in 2008. The couple didn’t realize until after they’d sent some bottles of wine to customers that it was tainted.
“We offered a bargain price if people wanted to keep the wine and didn't mind it, or we offered to give them a credit for the wine,” she said.
Many people opted for the credit, but Cahn said others actually liked the taste. It was novel at the time.
That may sound surprising, but Oberholster said she’s noticed this in her research, too: About a quarter of people are less sensitive to the taste and may not notice it at all. But she said the majority of people she’s surveyed do taste the smokiness, and there’s a level of taint where it’s likely no longer enjoyable for most.
“That ashy aftertaste is very hard to cover up,” Oberholster said. “And with aging of wine and as wine becomes a little bit less complex, that ashy character seems to just stand out more.”
In more recent years, Cahn says she’s had to reject shipments from growers she’s worked with for decades. Some, facing rejection from many vineyards, have quit.
“They have just said, you know, this has been too many years of not being able to make money on my vineyard, I don't think I want to do this anymore,” she said.
Cahn describes farming as a form of crisis management, even under normal conditions. But she sees smoke taint as one impact of climate change that will transform the industry permanently.
“We worry about climate warming as much as the forest fires and the smoke,” she said. “Some of the varieties that we planted [were] planted because the Anderson Valley was a really cool growing region, and that's changing.”
Cahn’s children, who already take part in running their business, will take over the rest of it once she and her husband retire. Already, she said their daughter has started making cheese from goat and sheep’s milk, which she sees as a welcome diversification of their products.
“Whenever you have a monoculture, there's a threat of it being really difficult to survive,” she said. “We're old, we don't have to worry about it too much longer, but our kids and our grandkids do.”
Oberholster sees the possibility for better, more viable options to treat tainted wine in the next couple of years. In the meantime, she says researchers have to investigate every possible solution — even the ones that might only help a little bit.
